// Definition for a binary tree node.
// #[derive(Debug, PartialEq, Eq)]
// pub struct TreeNode {
//   pub val: i32,
//   pub left: Option<Rc<RefCell<TreeNode>>>,
//   pub right: Option<Rc<RefCell<TreeNode>>>,
// }
//
// impl TreeNode {
//   #[inline]
//   pub fn new(val: i32) -> Self {
//     TreeNode {
//       val,
//       left: None,
//       right: None
//     }
//   }
// }
use std::rc::Rc;
use std::cell::RefCell;
impl Solution {
    fn reset(
        inorder: &Vec<i32>,
        i_left: usize,
        i_right: usize,
        postorder: &Vec<i32>,
        p_left: usize,
        p_right: usize
    ) -> Option<Rc<RefCell<TreeNode>>> {
        if i_left == i_right {
            return None;
        }
        let val = postorder[p_right - 1];
        let index = inorder
            .iter()
            .position(|&v| v == val)
            .unwrap();
        Some(
            Rc::new(
                RefCell::new(TreeNode {
                    val,
                    left: Self::reset(
                        inorder,
                        i_left,
                        index,
                        postorder,
                        p_left,
                        p_left + index - i_left
                    ),
                    right: Self::reset(
                        inorder,
                        index + 1,
                        i_right,
                        postorder,
                        p_left + index - i_left,
                        p_right - 1
                    ),
                })
            )
        )
    }

    pub fn build_tree(inorder: Vec<i32>, postorder: Vec<i32>) -> Option<Rc<RefCell<TreeNode>>> {
        let n = inorder.len();
        Self::reset(&inorder, 0, n, &postorder, 0, n)
    }
}
